User equipment and methods of bearer operation for carrier aggregation

ABSTRACT

Embodiments of a User Equipment (UE) to support dual-connectivity with a Master Evolved Node-B (MeNB) and a Secondary eNB (SeNB) are disclosed herein. The UE may receive downlink traffic packets from the MeNB and from the SeNB as part of a split data radio bearer (DRB). At least a portion of control functionality for the split DRB may be performed at each of the MeNB and the SeNB. The UE may receive an uplink eNB indicator for an uplink eNB to which the UE is to transmit uplink traffic packets as part of the split DRB. Based at least partly on the uplink eNB indicator, the UE may transmit uplink traffic packets to the uplink eNB as part of the split DRB. The uplink eNB may be selected from a group that includes the MeNB and the SeNB.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.15/994,154, filed May 31, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/917,154, filed Mar. 7, 2016, which is a U.S.National Stage Filing under 35 U.S.C. 371 from International ApplicationNo. PCT/US2014/063080, filed Oct. 30, 2014 and published in English asWO 2015/066281 on May 7, 2015, which claims the benefit of priority toU.S. Provisional Patent Application Ser. No. 61/898,425, filed Oct. 31,2013, each of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments pertain to wireless communications. Some embodiments relateto wireless networks including LTE networks. Some embodiments relate toCarrier Aggregation (CA) of multiple frequency bands. Some embodimentsrelate to CA arrangements using multiple Evolved Node-Bs (eNBs). Someembodiments relate to communication through split bearers.

BACKGROUND

Mobile networks may increase available bandwidth, throughput or capacityusing techniques such as carrier aggregation (CA), in which multiplefrequency bands may be supported simultaneously. As an example, a mobiledevice may communicate on multiple frequency bands with a single basestation. As another example, the mobile device may communicate tomultiple base stations on different frequency bands. Some associatedtasks, such as security and allocation of communication bearers, may bechallenging for CA arrangements, especially those in which multiple basestations are used. Accordingly, there is a general need for methods thatenable CA operation, and particularly CA operation with multiple basestations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of a 3GPP network in accordance with someembodiments;

FIG. 2 is a block diagram of a User Equipment (UE) in accordance withsome embodiments;

FIG. 3 is a block diagram of an Evolved Node-B (eNB) in accordance withsome embodiments;

FIG. 4 illustrates example user plane architectures for dualconnectivity Carrier Aggregation (CA);

FIG. 5 illustrates another example user plane architecture for dualconnectivity Carrier Aggregation (CA);

FIG. 6 illustrates the operation of a method of supportingdual-connectivity with a Master Evolved Node-B (MeNB) and a SecondaryeNB (SeNB) in accordance with some embodiments;

FIG. 7 illustrates a Radio Resource Control Information Element (RRC IE)DRB-ToAddMod in accordance with some embodiments; and

FIG. 8 illustrates the operation of another method of supportingdual-connectivity with an MeNB and an SeNB in accordance with someembodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

FIG. 1 is a functional diagram of a 3GPP network in accordance with someembodiments. The network comprises a radio access network (RAN) (e.g.,as depicted, the E-UTRAN or evolved universal terrestrial radio accessnetwork) 100 and the core network 120 (e.g., shown as an evolved packetcore (EPC)) coupled together through an S1 interface 115. Forconvenience and brevity sake, only a portion of the core network 120, aswell as the RAN 100, is shown.

The core network 120 includes mobility management entity (MME) 122,serving gateway (serving GW) 124, and packet data network gateway (PDNGW) 126. The RAN 100 includes Evolved Node-B's (eNBs) 104 (which mayoperate as base stations) for communicating with User Equipment (UE)102. The eNBs 104 may include macro eNBs and low power (LP) eNBs.

The MME is similar in function to the control plane of legacy ServingGPRS Support Nodes (SGSN). The MME manages mobility aspects in accesssuch as gateway selection and tracking area list management. The servingGW 124 terminates the interface toward the RAN 100, and routes datapackets between the RAN 100 and the core network 120. In addition, itmay be a local mobility anchor point for inter-eNB handovers and alsomay provide an anchor for inter-3GPP mobility. Other responsibilitiesmay include lawful intercept, charging, and some policy enforcement. Theserving GW 124 and the MME 122 may be implemented in one physical nodeor separate physical nodes. The PDN GW 126 terminates an SGi interfacetoward the packet data network (PDN). The PDN GW 126 routes data packetsbetween the EPC 120 and the external PDN, and may be a key node forpolicy enforcement and charging data collection. It may also provide ananchor point for mobility with non-LTE accesses. The external PDN can beany kind of IP network, as well as an IP Multimedia Subsystem (IMS)domain. The PDN GW 126 and the serving GW 124 may he implemented in onephysical node or separated physical nodes.

The eNBs 104 (macro and micro) terminate the air interface protocol andmay be the first point of contact for a UE 102. In some embodiments, aneNB 104 may fulfill various logical functions for the RAN 100 includingbut not limited to RNC (radio network controller functions) such asradio bearer management, uplink and downlink dynamic radio resourcemanagement and data packet scheduling, and mobility management. Inaccordance with some embodiments, UEs 102 may be configured tocommunicate OFDM communication signals with an eNB 104 over amulticarrier communication channel in accordance with an OFDMAcommunication technique. The OFDM signals may comprise a plurality oforthogonal subcarriers.

In accordance with some embodiments, a UE 102 may receive downlinktraffic packets from one or more eNBs 104 as part of a split data radiobearer (DRB). The UE 102 may also receive an uplink eNB indicator for anuplink eNB 104 to which the UE is to transmit uplink traffic packets aspart of the split DRB and may transmit uplink traffic packets to theuplink eNB 104 as part of the split DRB. The uplink eNB 104 may be thesame as or different from the eNB 104 from which the downlink trafficpackets are received. These embodiments are described in more detailbelow.

The S1 interface 115 is the interface that separates the RAN 100 and theEPC 120. It is split into two parts: the S1-U, which carries trafficdata between the eNBs 104 and the serving GW 124, and the S1-MME, whichis a signaling interface between the eNBs 104 and the MME 122. Inaddition, eNBs 104 may exchange signals or communicate over an interfacesuch as an X2 interface. The X2 interface comprises two parts, the X2-Cand X2-U. The X2-C is the control plane interface between the eNBs 104,while the X2-U is the user plane interface between the eNBs 104.

With cellular networks, LP cells are typically used to extend coverageto indoor areas where outdoor signals do not reach well, or to addnetwork capacity in areas with very dense phone usage, such as trainstations. As used herein, the term low power (LP) eNB refers to anysuitable relatively low power eNB for implementing a narrower cell(narrower than a macro cell) such as a femtocell, a picocell, or a microcell. Femtocell eNBs are typically provided by a mobile network operatorto its residential or enterprise customers. A femtocell is typically thesize of a residential gateway or smaller and generally connects to theuser's broadband line. Once plugged in, the femtocell connects to themobile operator's mobile network and provides extra coverage in a rangeof typically 30 to 50 meters for residential femtocells. Thus, a LP eNBmight be a femtocell eNB since it is coupled through the PDN GW 126.Similarly, a picocell is a wireless communication system typicallycovering a small area, such as in-building (offices, shopping malls,train stations, etc.), or more recently in-aircraft. A picocell eNB cangenerally connect through the X2 link to another eNB such as a macro eNBthrough its base station controller (BSC) functionality. Thus, LP eNBmay be implemented with a picocell eNB since it is coupled to a macroeNB via an X2 interface. Picocell eNBs or other LP eNBs may incorporatesome or all functionality of a macro eNB. In some cases, this may bereferred to as an access point base station or enterprise femtocell.

In some embodiments, a downlink resource grid may be used for downlinktransmissions from an eNB 104 to a UE 102, while uplink transmissionfrom the UE 102 to the eNB 104 may utilize similar techniques. The gridmay be a time-frequency grid, called a resource grid or time-frequencyresource grid, which is the physical resource in the downlink in eachslot. Such a time-frequency plane representation is a common practicefor OFDM systems, which makes it intuitive for radio resourceallocation. Each column and each row of the resource grid correspond toone OFDM symbol and one OFDM subcarrier, respectively. The duration ofthe resource grid in the time domain corresponds to one slot in a radioframe. The smallest time-frequency unit in a resource grid is denoted asa resource element. Each resource grid comprises a number of resourceblocks, which describe the mapping of certain physical channels toresource elements. Each resource block comprises a collection ofresource elements and in the frequency domain and represents thesmallest quanta of resources that currently can be allocated. There areseveral different physical downlink channels that are conveyed usingsuch resource blocks. With particular relevance to this disclosure, twoof these physical downlink channels are the physical downlink sharedchannel and the physical down link control channel.

The physical downlink shared channel (PDSCH) carries user data andhigher-layer signaling to a UE 102 (FIG. 1). The physical downlinkcontrol channel (PDCCH) carries information about the transport formatand resource allocations related to the PDSCH channel, among otherthings. It also informs the UE 102 about the transport format, resourceallocation, and H-ARQ information related to the uplink shared channel.Typically, downlink scheduling (assigning control and shared channelresource blocks to UEs 102 within a cell) is performed at the eNB 104based on channel quality information fed back from the UEs 102 to theeNB 104, and then the downlink resource assignment information is sentto a UE 102 on the control channel (PDCCH) used for (assigned to) the UE102.

The PDCCH uses CCEs (control channel elements) to convey the controlinformation. Before being mapped to resource elements, the PDCCHcomplex-valued symbols are first organized into quadruplets, which arethen permuted using a sub-block inter-leaver for rate matching. EachPDCCH is transmitted using one or more of these control channel elements(CCEs), where each CCE corresponds to nine sets of four physicalresource elements known as resource element groups (REGs). Four QPSKsymbols are mapped to each REG. The PDCCH can be transmitted using oneor more CCEs, depending on the size of DCI and the channel condition.There may be four or more different PDCCH formats defined in LTE withdifferent numbers of CCEs (e.g., aggregation level, L=1, 2, 4, or 8).

FIG. 2 is a block diagram of a User Equipment (UE) in accordance withsome embodiments. The UE 200 may be a UE 102 as depicted in FIG. 1. TheUE 200 may include Packet Data Convergence Protocol (PDCP) layercircuitry 202 for services such as security (ciphering and deciphering),header compression and decompression, and other services that may beperformed as part of operation with 3GPP or other standards. The UE 200may include Radio Link Control (RLC) layer circuitry 203 for servicessuch as concatenation, segmentation, reassembly and other services thatmay be performed as part of operation with 3GPP or other standards. TheUE 200 may include Medium Access Control layer (MAC) circuitry 204 forcontrolling access to the wireless medium. The UE 200 may includephysical layer (PHY) circuitry 205 for transmitting and receivingsignals to and from the eNB 300, other eNBs, other UEs or other devicesusing one or more antennas 201. The UE 200 may also include processingcircuitry 206 and memory 208 arranged to perform the operationsdescribed herein. In some embodiments, one or more of the above layers202-205 shown as part of the UE 200 may be associated with operation ofa primary cell and/or a secondary cell as part of Carrier Aggregation(CA), which will be described in more detail below.

FIG. 3 is a block diagram of an Evolved Node-B (eNB) in accordance withsome embodiments. The eNB 300 may be an eNB 104 as depicted in FIG. 1.The eNB 300 may include PDCP layer circuitry 302 for services such assecurity (ciphering and deciphering), header compression anddecompression, and other services that may he performed as part ofoperation with 3GPP or other standards. The eNB 300 may include RLClayer circuitry 303 for services such as concatenation, segmentation,reassembly and other services that may be performed as part of operationwith 3GPP or other standards. The eNB 300 may include MAC layercircuitry 304 for controlling access to the wireless medium. The eNB 300may include physical layer (PHY) circuitry 305 for transmitting andreceiving signals to and from the UE 200, other UEs, other eNBs or otherdevices using one or more antennas 301. The eNB 300 may also includeprocessing circuitry 306 and memory 308 arranged to perform theoperations described herein. In some embodiments, one or more of theabove layers 302-305 shown as part of the eNB 300 may be associated withoperation of a primary cell and/or a secondary cell as part of CarrierAggregation (CA), which will be described in more detail below.

In some embodiments, mobile devices or other devices described hereinmay be part of a portable wireless communication device, such as apersonal digital assistant (PDA), a laptop or portable computer withwireless communication capability, a web tablet, a wireless telephone, asmartphone, a wireless headset, a pager, an instant messaging device, adigital camera, an access point, a television, a medical device (e.g., aheart rate monitor, a blood pressure monitor, etc.), or other devicethat may receive and/or transmit information wirelessly. In someembodiments, the mobile device or other device can be the UE 200 or theeNB 300 configured to operate in accordance with 3GPP standards. In someembodiments, the mobile device or other device may be configured tooperate according to other protocols or standards, including IEEE 802.11or other IEEE standards. In some embodiments, the mobile device or otherdevice may include one or more of a keyboard, a display, a non-volatilememory port, multiple antennas, a graphics processor, an applicationprocessor, speakers, and other mobile device elements. The display maybe an LCD screen including a touch screen.

The antennas 201, 301 may comprise one or more directional oromnidirectional antennas, including, for example, dipole antennas,monopole antennas, patch antennas, loop antennas, microstrip antennas orother types of antennas suitable for transmission of RF signals. In somemultiple-input multiple-output (MIMO) embodiments, the antennas 201, 301may be effectively separated to take advantage of spatial diversity andthe different channel characteristics that may result.

Although the UE 200 and eNB 300 are each illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, some elements may comprise one or more microprocessors, DSPs,field-programmable gate arrays (FPGAs), application specific integratedcircuits (ASICs), radio-frequency integrated circuits (RFICs) andcombinations of various hardware and logic circuitry for performing atleast the functions described herein. In some embodiments, thefunctional elements may refer to one or more processes operating on oneor more processing elements.

Embodiments may be implemented in one or a combination of hardware,firmware and software. Embodiments may also be implemented asinstructions stored on a computer-readable storage device, which may beread and executed by at least one processor to perform the operationsdescribed herein. A computer-readable storage device may include anynon-transitory mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a computer-readable storagedevice may include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and other storage devices and media. Some embodiments mayinclude one or more processors and may be configured with instructionsstored on a computer-readable storage device.

In accordance with embodiments, the UE 102 may support dual-connectivitywith a Master eNB (MeNB) 104 and a Secondary eNB (SeNB) 104. The UE 102may receive downlink traffic packets from the SeNB 104 as part of asplit data radio bearer (DRB). In addition, the UE 102 may also receivedownlink traffic packets from the MeNB 104 as part of the split DRB. Atleast a portion of control functionality for the split DRB may beperformed at each of the MeNB 104 and the SeNB 104. The UE 102 mayreceive an uplink eNB indicator for an uplink eNB 104 to which the UE102 is to transmit uplink traffic packets as part of the split DRB.Based at least partly on the uplink eNB indicator, the UE 102 maytransmit uplink traffic packets to the uplink eNB 104 as part of thesplit DRB. The uplink eNB 104 may be selected from a group of candidateeNBs that includes the MeNB 104 and the SeNB 104. These embodiments aredescribed in more detail below.

In some scenarios, the performance, throughput or capacity for a systemmay be improved or increased through the use of Carrier Aggregation(CA), in which multiple frequency bands may be utilized by eNBs 104 andUEs 102 to exchange control information and traffic packets. As anexample, the control information may include mobility information orsecurity input while the traffic packets may include data, voice orother content. One of the frequency bands may be associated with aPrimary Cell (PCell), which may be used to exchange control information.In some embodiments, the PCell may also be used to transmit trafficpackets. An eNB 104 that supports the PCell may be referred to as a“Master eNB” or “MeNB.” in addition, one or more Secondary Cells(SCells) may be configured on other frequency bands to operatecooperatively with the PCell for exchanging traffic packets. The PCelland the SCell may operate according to 3GPP standards in someembodiments.

It should be noted that throughout this disclosure, an MeNB and/or SeNBmay be referred to as an eNB 104 as depicted in FIG. 1 for illustrativepurposes. This is not limiting, however, and it is understood that aneNB 104 may be configured as an MeNB, an SeNB or either in some cases.In addition, reference to the MeNB and SeNB by the same number 104 isnot limiting.

In some embodiments, one or more of the SCells may be assigned to an eNB104 different from the MeNB. Accordingly, an eNB 104 that supports oneor more SCells for the UE 102, but does not support the PCell for the UE102, may be referred to as a “Secondary eNB” or “SeNB.” Such CAarrangements in which the LB 102 is served by one or more SeNBs 104 (inaddition to the MeNB 104) may be referred to as “dual connectivity.” inaddition, such CA arrangements may also be referred to as “inter-eNB CA”or “inter-node resource aggregation.” These embodiments will bedescribed in more detail below. It should be noted that embodimentsdescribed herein are not limited in terms of the number of Scellsconfigured or the number of SeNBs 104 used in a CA scenario or CAexample. Although discussion below may describe CA scenarios thatinclude an MeNB 104 and a single SeNB 104 supporting a single SCell,this is done for ease of illustration only, and is not limiting.

FIG. 4 illustrates example user plane architectures for dualconnectivity Carrier Aggregation (CA). In the examples shown, one ormore S1-U interfaces previously described may connect a Serving GW 124to eNBs 104, which may include an MeNB 410 and an SeNB 420. The MeNB 410and SeNB 420 both may exchange traffic packets with the UE 102 as partof the CA operation. In the “non-bearer split” arrangement 400, the S1-Uinterface 411 may connect the Serving GW 124 and the MeNB 410 as part ofa bearer for a PCell. Accordingly, the MeNB 410 may performfunctionality for layers such as PDCP 412, RLC 413, and MAC 414 for thebearer for the PCell. In addition, the S1-U interface 421 may connectthe Serving GW 124 and the SeNB 420 as part of a bearer for an SCell.The SeNB 420 may perform functionality for layers such as PDCP 422, RLC423, and MAC 424 for the bearer for the SCell. In non-bearer splitarrangements such as 400, the SeNB 420 may perform security tasks suchas distribution and/or management of security keys.

In the “bearer split” arrangement 450, the S1-U interface 461 mayconnect the Serving GW 124 and the MeNB 460 as part of a bearer for aPCell, and the MeNB 460 may perform functionality for layers such asPDCP 462, RLC 463, and MAC 464 for the bearer for the PCell. Inaddition, an SCell may be supported on the SeNB 470 through a bearerthat is split between the MeNB 460 and the SeNB 470. Accordingly, theS1-U interface 471 may connect the Serving GW 124 and the MeNB 420 andthe MeNB 420 may perform functions related to the PDCP layer 472 as partof the bearer for the SCell. The SeNB 470 may perform functions relatedto the RLC layer 473 and MAC layer 474 as part of the bearer for theSCell. The Xn interface 480 may be used for exchanging data or packetsbetween the MeNB 460 and SeNB 470 as part of the bearer splitarrangement. In bearer split arrangements such as 450, as the MeNB 460may perform functions for the PDCP layer 472, the SeNB 470 may not needto handle security tasks such as distribution and/or management ofsecurity keys.

Various challenges may arise in arrangements such as 400 or 450 orothers that support CA with multiple eNBs 104. Some examples ofchallenges and techniques for addressing the challenges will beaddressed below.

In a first challenge, the UE 102 supporting CA may be configured with afirst bearer in a bearer split arrangement (such as 450) with an MeNB104 and a first SeNB 104. As previously described, the MeNB 104 mayhandle security aspects for the first hearer, and therefore a securitykey associated with the UE 102 may not be made available to the firstSeNB 104. As part of the CA, the UE 102 may be configured with anadditional second bearer in a non-bearer split arrangement such as 400with the MeNB 104 and a second. SeNB 104. As previously described fornon-bearer split arrangements, the second SeNB 104 may handle or mayneed to handle security aspects for the second bearer. However, thesecurity key for the UE 102 may not be available to SeNBs 104 operatingas part of the CA for various reasons. Accordingly, the SeNB 104 may nothave the flexibility to support a non-bearer split arrangement, and maybe restricted to a bearer split arrangement for the new bearer.

A method for addressing the first challenge is described below. For anSeNB 104 that already supports one or more radio bearers, when a newradio bearer is established in the SeNB 104, the MeNB 104 may transmit asecurity key or security information to the SeNB 104. Accordingly, thenon-bearer split option for the new bearer may be used, and the SeNB 104may be able to provide necessary security functions for the new bearerby utilizing the security key or security information. That is, the SeNB104 may be provided with flexibility to handle bearer split ornon-bearer split configurations. The MeNB 104 may use an XnAP message orother message to transmit security keys or other security information tothe SeNB 104 as part of the method. In some embodiments, a message thatis also used to establish the radio bearer may be used. As an example, asecurity key such as a KeNB may be transmitted for use at the SeNB 104for providing security functions for the new bearer. The security keytransmitted to the SeNB 104 may be the same as a key used by the MeNB104 for security functions at the MeNB 104, for instance as part of aPCell. However, the security key transmitted to the SeNB 104 is not solimited, and may be different from security keys used at the MeNB 104 insome cases.

In a second challenge, an SeNB 104 may support multiple SCells, eitherfor the UE 102 or for the UE 102 and other UEs. For a non-bearer splitconfiguration such as 400, a security key may be available to the SeNB104 and may be used by the SeNB 104 for providing security functionssuch as in the PDCP layer 422 in the appropriate SCell. A key refreshprocedure may be performed when a counter (such as a “PDCP COUNT” orsimilar in 3GPP or other standards) is about to wrap-around, reset orexpire. However, when the SeNB 104 supports additional SCells, a keyrefresh procedure may be challenging. In addition, determination of atime at which such a key refresh procedure may take place or conditionsor events to trigger such a key refresh procedure may be challenging.

A method for addressing the second challenge is described below. For anSeNB 104 that supports multiple SCells, a key refresh procedure may takeplace for all SCells supported by the SeNB 104 when at least one of thePDCP COUNT counters is about to wrap-around, reset or expire. In someembodiments, when a PDCP COUNT counter of at least one of the SCells iswithin a predetermined margin of a wrap-around count value, a keyrefresh procedure may be implemented for all the SCells. The MeNB 104may initiate the procedure by sending one or more messages to the SeNB104, in some embodiments. The procedure may also be performedautomatically by the SeNB 104 in some embodiments.

In a third challenge, downlink reception at the UE 102 may includereception of traffic packets on a split bearer from multiple eNBs 104(an MeNB 104 and one or more SeNBs 104). As an example, the UE 102 maysupport a bearer in a bearer split configuration between the MeNB 104and an SeNB 104. Accordingly, the UE 102 may perform RLC functionality(for instance, block 203 from FIG. 2) for downlink reception of trafficpackets independently for the MeNB 104 and the SeNB 104. That is, the UE102 may pass a received packet from the RLC layer 203 to the PDCP layer202 regardless of the eNB 104 (MeNB 104 or SeNB 104) from which thepacket is received. Accordingly, packets arriving at the PDCP layer 202from the RLC layer 203 may be out of sequence. When the PDCP layer 202detects that a packet has arrived out of sequence, it may start a PDCPreordering timer, such as a “pdcp-t-Reordering” timer of 3GPP or otherstandards. Upon expiration of the PDCP reordering timer, or in responseto the expiration, the PCDP layer 202 may pass the out-of-sequencepackets to an upper layer. As a result of the bearer splitconfiguration, if one of the eNBs 104 (MeNB or SeNB) does not transmitdata for reception at the UE 102, the PDCP reordering process may causeunnecessary delay. For instance, the PDCP layer 202 may essentially bewaiting for packets with a certain sequence number or index to complywith reordering, although such packets may not have even beentransmitted to the UE 102.

A method for addressing the third challenge is described below. For a UE102 that supports a bearer in a bearer split configuration between theMeNB 104 and the SeNB 104, a PDCP reordering timer at the UE 102 maytake the value of zero. That is, the PDCP reordering timer may bedisabled or bypassed in some embodiments. Accordingly, when bearer datais transmitted from only one of the MeNB 104 and SeNB 104 during a timeperiod, PDCP reordering may be unnecessary and may introduce additionaldelay in passing the received packets from the PDCP layer 202 to upperlayers. Setting the value of the PDCP reordering timer to zero, orbypassing or disabling the PDCP reordering timer, may enable processedPDCP data to be delivered to upper layers without the additional delayfrom the PDCP reordering. As such, setting the value of the PDCPreordering timer to zero, or bypassing or disabling the PDCP reorderingtimer, may be an optimization or an improvement. In some embodiments,one of the eNBs 104 may enable or disable PDCP reordering, or may setPDCP reordering timer value(s) to zero, for multiple bearersindividually in a flexible arrangement.

In a fourth challenge, the UE 102 may support a CA arrangement thatincludes operation with a bearer according to a split bearerconfiguration with an MeNB 104 and an SeNB 104. Accordingly, theoperation may include transmission of uplink packets by the UE 102 andreception of downlink packets at the UE 102 as part of the bearer. Iftransmission of the uplink traffic packets by the UE 102 is restrictedto the SeNB 104, the lack of flexibility regarding the uplinktransmission may present challenges for the UE 102 and/or the network.As an example scenario, the SeNB 104 may transmit downlink trafficpackets to the UE 102 as part of the bearer, but it may be better forthe UE 102 to transmit uplink traffic packets for the bearer to the MeNB104 instead of the SeNB 104. In some cases, the SeNB 104 may havelimited uplink spectrum despite having sufficient downlink spectrum.

A method for addressing the fourth challenge is described below. Whenthe network configures a bearer split configuration for a bearer betweenthe UE 102 and the MeNB 104 and the SeNB 104, the network may alsoconfigure to which eNB 104 (of the MeNB or SeNB) the UE 102 is totransmit uplink traffic packets as part of the bearer. Accordingly, abearer setup message may be received at the UE 102. The bearer setupmessage may be transmitted by the MeNB 104 in some embodiments. Itshould be noted that the bearer setup message may or may not be amessage specifically intended for the establishment of the bearer, butis not so limited. In some embodiments, the bearer setup message mayrefer to another control message intended for other purposes, andcontrol information related to the establishment of the bearer may betransported by the control message. In any case, the bearer setupmessage may include an uplink eNB indicator related to which eNB 104 theUE 102 is to transmit uplink traffic packets.

In some embodiments, the eNB 104 to which the UE 102 is to transmituplink traffic packets may be selected from a group of eNBs 104 thatincludes the MeNB 104 and the SeNB 104. That is, the uplink eNBindicator may indicate which of the MeNB 104 or SeNB 104 that the UE 102is to transmit uplink traffic packets. As an example, the uplink eNBindicator may be a binary indicator with the two options of MeNB 104 orSeNB 104. Such embodiments are not limiting, however, as the uplink eNBindicator may include any indicator(s) or parameter(s) that may conveyinformation to the UE 102 about an eNB 104 to which the UE 102 is totransmit uplink traffic packets as part of the bearer.

In addition, as part of the method, the UE 102 may transmit one or moreRLC Status PDUs to the eNB 104 to which the network has instructed theUE 102 to transmit uplink traffic packets as part of the bearer. As anexample, the RLC Status PDUs may be transmitted to one of the MeNB 104or SeNB 104.

FIG. 5 illustrates another example user plane architecture for dualconnectivity Carrier Aggregation (CA). Continuing with the previousexample related to the fourth challenge above, at the UE 102, a splitbearer may include functionality performed by the PDCP 505, RLC 510, andMAC 515 when the UE 102 is configured to transmit uplink traffic packetsto the SeNB 104. As an alternative, when the UE 102 is configured totransmit uplink traffic packets to the MeNB 104, functionality may beperformed by the PDCP 505, RLC 525, and MAC 530. It should be recalledthat the UE 102 may also support a bearer related to the which includesexchanging packets between the UE 102 and the MeNB 104. Suchfunctionality for the PCell bearer may be performed by the MAC 530, RLC540, and PDCP 545.

FIG. 6 illustrates the operation of a method of supportingdual-connectivity with a Master Evolved Node-B (MeNB) 104 and aSecondary eNB (SeNB) 104 in accordance with some embodiments. It isimportant to note that embodiments of the method 600 may includeadditional or even fewer operations or processes in comparison to whatis illustrated in FIG. 6. In addition, embodiments of the method 600 arenot necessarily limited to the chronological order that is shown in FIG.6. In describing the method 600, reference may be made to FIGS. 1-5 and7-8, although it is understood that the method 600 may be practiced withany other suitable systems, interfaces and components.

In addition, while the method 600 and other methods described herein mayrefer to eNBs 104 or UEs 102 operating in accordance with 3GPP or otherstandards, embodiments of those methods are not limited to just thoseeNBs 104 or UEs 102 and may also be practiced on other mobile devices,such as a Wi-Fi access point (AP) or user station (STA). Moreover, themethod 600 and other methods described herein may be practiced bywireless devices configured to operate in other suitable types ofwireless communication systems, including systems configured to operateaccording to various IEEE standards such as IEEE 802.11.

At operation 605 of the method 600, the UE 102 may exchange controlmessages with an MeNB 104 on a Primary Cell (PCell) included in a MasterCell Group (MCG) supported by the MeNB 104. The control messages may berelated to establishment of communication sessions, radio bearers orother control tasks.

At operation 610, the UE 102 may receive downlink traffic packets fromthe MeNB and from an SeNB 104 as part of a split data radio bearer(DRB). Accordingly, at least a portion of control functionality for thesplit DRB may be performed at each of the MeNB 104 and the SeNB 104. Atoperation 615, the UE 102 may receive a Radio Resource Control (RRC)message that includes an uplink eNB indicator for an uplink eNB 104 towhich the UE 102 is to transmit uplink traffic packets as part of thesplit DRB. At operation 620, uplink traffic packets may be transmittedto the uplink eNB 104 as part of the split DRB. At operation 625, the UE102 may transmit, for reception at the uplink eNB 104, a Radio LinkControl (RLC) status Protocol Data Unit (PDU) that includes statusinformation for the split DRB.

In some embodiments, the uplink eNB 104 may be selected from a group ofcandidate eNBs 104 that includes the MeNB 104 and the SeNB 104. In someembodiments, the uplink eNB 104 may be different from the SeNB 104. Aspreviously described, it may be beneficial or necessary in some casesthat the uplink traffic and downlink traffic for the DRB be sent todifferent eNBs 104, and that discussion may apply to the method 600. Insome embodiments, the eNB 104 to which the uplink traffic packets aretransmitted may be based at least partly on the uplink eNB indicator. Insome embodiments, the uplink traffic packets may include one or morePacket Data Convergence Protocol (PDCP) Service Data Units (SDUs),although not limited as such.

In some embodiments, the split DRB may operate as part of a SecondaryCell (SCell) included in a Secondary Cell Group (SCG) supported by theSeNB 104 and the uplink eNB indicator may indicate whether the UE 102 isto transmit uplink traffic packets on the SCG or the MCG. Accordingly,the eNB indicator in these embodiments may perform the samefunctionality as the eNB indicator described earlier that may indicatewhich of the MeNB 104 or SeNB 104 to which the uplink traffic packetsshould be transmitted.

FIG. 7 illustrates a Radio Resource Control Information Element (RRC IE)DRB-ToAddMod in accordance with some embodiments. In some embodiments,the RRC message that includes the uplink eNB indicator may be or mayinclude an information element such as the RRC IF DRB-ToAddMod 700.However, it is understood that the RRC IE DRB-ToAddMod 700 is shown anddescribed for illustrative purposes, and is not limiting. Accordingly,the RRC message may be of a different form that may or may not includesome or all of the information included in the RRC DRB-ToAddMod 700. Inaddition, the organization of the RRC message is not limited to thatshown in FIG. 7, as some or all of the information or parameters shownmay be combined or divided but still included in the RRC message.

Information or parameters of the RRC IE DRB-ToAddMod 700 may include,but are not limited to, the EPS bearer identity 705, the DRB identity710, the PDCP Config IE 715, the RLC Config IE 720, the Logical ChannelIdentity 725, the Logical Channel Config IE 730, and the UL-BearerEnbparameter 735. In addition, the RRC IE DRB-ToAddMod 700 may or may notinclude other parameters or information 740.

In this example, the UL-BearerEnb parameter 735 may indicate the eNB 104to which the UE 102 is to transmit uplink packets. Accordingly, theUL-BearerEnb parameter 735 may be or may serve the same functionality asthe uplink eNB indicator previously described. As an example, theUL-BearerEnb parameter 735 may take on the values of “MeNB” or “SeNB” toindicate the eNB 104 to which the UE 102 is to transmit uplink packets.

At operation 630, the UE 102 may exchange traffic packets with the MeNB104 on the PCell as part of a second, different DRB. Accordingly, aspart of the CA arrangement, the UE 102 may support both DRBssimultaneously, and may even support more DRBs in some cases.

It should be pointed out that the method 600 may be used to address thefourth challenge previously described, although not limited as such.Accordingly, some or all of the discussion related to either theprevious method for addressing the fourth challenge or to the method 600may apply to the other method in some cases. In addition, someembodiments may include techniques or operations from either or both ofthese methods or other methods disclosed herein.

FIG. 8 illustrates the operation of another method of supportingdual-connectivity with an MeNB and an SeNB in accordance with someembodiments. In some embodiments, the method 800 may be practiced at theUE 102, but is not limited as such. As mentioned previously regardingthe method 600, embodiments of the method 800 may include additional oreven fewer operations or processes in comparison to what is illustratedin FIG. 8 and embodiments of the method 800 are not necessarily limitedto the chronological order that is shown in FIG. 8. In describing themethod 800, reference may be made to FIGS. 1-7, although it isunderstood that the method 800 may be practiced with any other suitablesystems, interfaces and components. In addition, embodiments of themethod 800 may refer to eNBs 104, UEs 102, APs, STAs or other wirelessor mobile devices.

At operation 805 of the method 800, the UE 102 may receive downlinktraffic packets from the SeNB 104 as part of a split data radio bearer(DRB). As previously described, at least a portion of controlfunctionality for the split DRB may be performed at each of the MeNB 104and the SeNB 104. At operation 810, the UE 102 may receive downlinktraffic packets from the MeNB 104 as part of the split DRB. Accordingly,the UE 102 may support the split DRB as part of a CA arrangement. Inorder to pass the downlink traffic packets to layers above the PDCPlayer, a PDCP layer reordering may be used. At operation 815, the UE 102may bypass a PDCP reordering timer as part of the PDCP layer reorderingfor the received downlink traffic packets. In some embodiments, the PDCPreordering timer may control a minimum waiting period for which the UE102 monitors for downlink traffic packets received out of sequence. Insome embodiments, the PDCP reordering timer may be set to a value ofzero as part of the bypass.

It should be pointed out that the method 800 may be used to address thethird challenge previously described, although not limited as such.Accordingly, some or all of the discussion related to either theprevious method for addressing the third challenge or to the method 800may apply to the other method in some cases. In addition, someembodiments may include techniques or operations from either or both ofthese methods or other methods disclosed herein.

User Equipment (UE) to support dual-connectivity with a Master EvolvedNode-B (MeNB) and a Secondary eNB (SeNB) is disclosed herein. The UE maycomprise hardware processing circuitry configured to receive downlinktraffic packets from the MeNB and from the SeNB as part of a split dataradio bearer (DRB). In some embodiments, at least a portion of controlfunctionality for the split DRB may be performed at each of the MeNB andthe SeNB. The hardware processing circuitry may be further configured toreceive a Radio Resource Control (RRC) message that includes an uplinkeNB indicator for an uplink eNB to which the UE is to transmit uplinktraffic packets as part of the split DRB. The hardware processingcircuitry may be further configured to transmit, based at least partlyon the uplink eNB indicator, uplink traffic packets to the uplink eNB aspart of the split DRB. In some embodiments, the uplink eNB may beselected from a group of candidate eNBs that includes the MeNB and theSeNB. In some embodiments, the uplink eNB may be different from theSeNB.

The hardware processing circuitry may be further configured to exchangecontrol messages with the MeNB on a Primary Cell (PCell) included in aMaster Cell Group (MCG) supported by the MeNB. In some embodiments, thesplit DRB may operate as part of a Secondary Cell (SCell) included in aSecondary Cell Group (SCG) supported by the SeNB. In some embodiments,the uplink eNB indicator may indicate whether the UE is to transmituplink traffic packets on the SCG or the MCG. In some embodiments, theuplink traffic packets may include one or more Packet Data ConvergenceProtocol (PDCP) Service Data Units (SDUs). The hardware processingcircuitry may be further configured to exchange traffic packets with theMeNB on the PCell as part of a second, different DRB. The hardwareprocessing circuitry may be further configured to transmit, forreception at the uplink eNB, a Radio Link Control (RLC) status ProtocolData Unit (PDU) that includes status information for the split DRB.

A non-transitory computer-readable storage medium that storesinstructions for execution by one or more processors to performoperations for support, by User Equipment (UE), of dual-connectivitywith a Master Evolved Node-B (MeNB) and a Secondary eNB (SeNB) is alsodisclosed herein. The operations may configure the one or moreprocessors to receive downlink traffic packets from the MeNB and fromthe SeNB as part of a split data radio bearer (DRB). In someembodiments, at least a portion of control functionality for the splitDRB may be performed at each of the MeNB and the SeNB. The operationsmay configure the one or more processors to receive a Radio ResourceControl (RRC) message that includes an uplink eNB indicator for anuplink eNB to which the UE is to transmit uplink traffic packets as partof the split DRB. The operations may configure the one or moreprocessors to transmit, based at least partly on the uplink eNBindicator, uplink traffic packets to the uplink eNB as part of the splitDRB. In some embodiments, the uplink eNB may be selected from a group ofcandidate eNBs that includes the MeNB and the SeNB.

The operations may further configure the one or more processors toexchange control messages with the MeNB on a Primary Cell (PCell)included in a Master Cell Group (MCG) supported by the MeNB. In someembodiments, the split DRB may operate as part of a Secondary Cell(SCell) included in a Secondary Cell Group (SCG) supported by the SeNB.In some embodiments, the uplink eNB indicator may indicate whether theUE is to transmit uplink traffic packets on the SCG or the MCG. In someembodiments, the uplink traffic packets may include one or more PacketData Convergence Protocol (PDCP) Service Data Units (SDUs).

A method of supporting dual-connectivity with a Master Evolved Node-B(MeNB) and a Secondary eNB (SeNB) at User Equipment (UE) is alsodisclosed herein. The method may include receiving downlink trafficpackets from the MeNB and from the SeNB as part of a split data radiobearer (DRB). In some embodiments, at least a portion of controlfunctionality for the split DRB may be performed at each of the MeNB andthe SeNB. The method may further include receiving a Radio ResourceControl (RRC) message that includes an uplink eNB indicator for anuplink eNB to which the UE is to transmit uplink traffic packets as partof the split DRB. The method may further include transmitting, based atleast partly on the uplink eNB indicator, uplink traffic packets to theuplink eNB as part of the split DRB. In some embodiments, the uplink eNBmay be selected from a group of candidate eNBs that includes the MeNBand the SeNB.

The method may further include exchanging control messages with the MeNBon a Primary Cell (PCell) included in a Master Cell Group (MCG)supported by the MeNB. In some embodiments, the split DRB may operate aspart of a Secondary Cell (SCell) included in a Secondary Cell Group(SCG) supported by the SeNB. In some embodiments, the uplink eNBindicator may indicate whether the UE is to transmit uplink trafficpackets on the SCG or the MCG. In some embodiments, the uplink trafficpackets may include one or more Packet Data Convergence Protocol (PDCP)Service Data Units (SDUs).

User Equipment (UE) to support dual-connectivity with a Master EvolvedNode-B (MeNB) and a Secondary eNB (SeNB) is also disclosed herein. TheUE may comprise hardware processing circuitry configured to receivedownlink traffic packets from the MeNB and from the SeNB as part of asplit data radio bearer (DRB). In some embodiments, at least a portionof control functionality for the split DRB may be performed at each ofthe MeNB and the SeNB. The hardware processing circuitry may be furtherconfigured to receive downlink traffic packets from the MeNB as part ofa second, different DRB. The hardware processing circuitry may befurther configured to bypass, as part of PDCP layer reordering for thereceived downlink traffic packets, a PDCP reordering timer that controlsa minimum waiting period for which the UE monitors for downlink trafficpackets received out of sequence. In some embodiments, the PDCPreordering timer may be set to a value of zero as part of the bypass.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims. The following claims are hereby incorporatedinto the detailed description, with each claim standing on its own as aseparate embodiment.

1. (canceled)
 2. An apparatus of a user equipment (UE) configured fordual connectivity with a master base station and a secondary basestation, the apparatus comprising: a processor configured to cause theUE to: decode downlink traffic packets received from the master basestation and from the secondary base station as part of a split dataradio bearer (DRB); decode Radio Resource Control (RRC) signalingreceived from the master base station, the RRC signaling including: afirst indicator specifying whether the UE is to transmit uplink trafficpackets only to the master base station; and a second indicatorspecifying a Packet Data Convergence Protocol (PDCP) timer forreordering downlink traffic packets received out of sequence as part ofthe split DRB; and based at least partly on the first indicator, encodea first uplink traffic packet of the uplink traffic packets fortransmission to the master base station or the secondary base station aspart of the split DRB.
 3. The apparatus of claim 2, wherein the downlinktraffic packets include one or more PDCP Service Data Units (SDUs). 4.The apparatus of claim 2, wherein the processor is further configured tocause the UE to exchange traffic packets with the master base station aspart of a second, different DRB.
 5. The apparatus of claim 2, whereinthe processor is further configured to cause the UE to transmit statusinformation for the split DRB.
 6. The apparatus of claim 5, wherein thestatus information for the split DRB is transmitted in a Radio LinkControl (RLC) status Protocol Data Unit (PDU).
 7. The apparatus of claim6, wherein the RLC status PDU is transmitted to the master base station.8. The apparatus of claim 6, wherein the RLC status PDU is transmittedto the secondary base station.
 9. A user equipment (UE) configured fordual connectivity with a master base station and a secondary basestation, the UE comprising: a radio; and a processor operably connectedto the radio and configured to cause the UE to: decode downlink trafficpackets received from the master base station and from the secondarybase station as part of a split data radio bearer (DRB); decode RadioResource Control (RRC) signaling received from the master base station,the RRC signaling including: a first indicator specifying whether the UEis to transmit uplink traffic packets only to the master base station;and a second indicator specifying a Packet Data Convergence Protocol(PDCP) timer for reordering downlink traffic packets received out ofsequence as part of the split DRB; and based at least partly on thefirst indicator, encode a first uplink traffic packet of the uplinktraffic packets for transmission to the master base station or thesecondary base station as part of the split DRB.
 10. The UE of claim 9,wherein the downlink traffic packets include one or more PDCP ServiceData Units (SDUs).
 11. The UE of claim 9, wherein the processor isfurther configured to cause the UE to exchange traffic packets with themaster base station as part of a second, different DRB.
 12. The UE ofclaim 9, wherein the processor is further configured to cause the UE totransmit status information for the split DRB.
 13. The UE of claim 12,wherein the status information for the split DRB is transmitted in aRadio Link Control (RLC) status Protocol Data Unit (PDU).
 14. The UE ofclaim 13, wherein the RLC status PDU is transmitted to the master basestation.
 15. The UE of claim 13, wherein the RLC status PDU istransmitted to the secondary base station.
 16. A method for operating auser equipment (UE) configured for dual connectivity with a master basestation and a secondary base station, the method comprising: at the UE:decoding downlink traffic packets received from the master base stationand from the secondary base station as part of a split data radio bearer(DRB); decoding Radio Resource Control (RRC) signaling received from themaster base station, the RRC signaling including: a first indicatorspecifying whether the UE is to transmit uplink traffic packets only tothe master base station; and a second indicator specifying a Packet DataConvergence Protocol (PDCP) timer for reordering downlink trafficpackets received out of sequence as part of the split DRB; and based atleast partly on the first indicator, encoding a first uplink trafficpacket of the uplink traffic packets for transmission to the master basestation or the secondary base station as part of the split DRB.
 17. Themethod of claim 16, wherein the downlink traffic packets include one ormore PDCP Service Data Units (SDUs).
 18. The method of claim 16, furthercomprising exchanging traffic packets with the master base station aspart of a second, different DRB.
 19. The method of claim 16, furthercomprising transmitting status information for the split DRB.
 20. Themethod of claim 16, wherein the status information for the split DRB istransmitted in a Radio Link Control (RLC) status Protocol Data Unit(PDU).
 21. The method of claim 20, wherein the RLC status PDU istransmitted to the master base station and the secondary base station.